If property’s OnMeasureImage returns size that has height != 0 but less than row height ( < 0 has special meanings), wx.propgrid.PropertyGrid calls this method to draw a custom image in a limited area in front of the editor control or value text/graphics, and if control has drop-down list, then the image is drawn there as well (even in the case OnMeasureImage returned higher height than row height).

NOTE: Following applies when OnMeasureImage returns a “flexible” height ( using PG_FLEXIBLE_SIZE(W,H) macro), which implies variable height items: If rect.x is < 0, then this is a measure item call, which means that dc is invalid and only thing that should be done is to set paintdata.m_drawnHeight to the height of the image of item at index paintdata.m_choiceItem. This call may be done even as often as once every drop-down popup show.